Re: Topband: RX/TX Antenna decoupling, (OFF LIST)

[HAROLD SMITH JR]

Sorry to let you know that a brilliant light that was Price was dimmed on the 
21st. Price is a silent key now. He will be missed.XYL  Inge

  From: Rob Atkinson <ranchoro...@gmail.com>
 To: topband@contesting.com 
 Sent: Friday, October 6, 2017 5:15 AM
 Subject: Re: Topband: RX/TX Antenna decoupling, (OFF LIST)
   
> Thanks for sharing this info.
> Would you please provide more information on the relay model number and how
> it is wired into your system.

I used a P open frame relay 4PDT but a single throw will work.
What's important is that the relay use metal other than steel (or
other magnetic metal) for the RF path.  The P PM17DY satisfies this
requirement.  I mounted it in a plastic box and mounted UHF jacks on
the ends and ran copper strap and AWG10 stranded to the relay, using
the AWG10 for the center conductor.  I used two poles for the center
and two for the cable shield.  On rx the relay is open and the
inverted L is disconnected from the shack and common mode RF prevented
from continuing to the shack.  The plastic box is important for this
-- a typical metal box would allow the shield RF to continue from the
UHF jack flanges around the relay at all times.  The relay I used has
a 24 v. coil because my T/R sequencing system runs on a 24 v. DC
supply.  This as all antenna relays should be used with a sequencer to
avoid hot switching.  Obviously this is not a solution if one desires
QSK.  In that case a faster switch is needed.

73

Rob
K5UJ
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Re: Topband: RX/TX Antenna decoupling, (OFF LIST)

[Rob Atkinson]

> Thanks for sharing this info.
> Would you please provide more information on the relay model number and how
> it is wired into your system.

I used a P open frame relay 4PDT but a single throw will work.
What's important is that the relay use metal other than steel (or
other magnetic metal) for the RF path.  The P PM17DY satisfies this
requirement.  I mounted it in a plastic box and mounted UHF jacks on
the ends and ran copper strap and AWG10 stranded to the relay, using
the AWG10 for the center conductor.  I used two poles for the center
and two for the cable shield.  On rx the relay is open and the
inverted L is disconnected from the shack and common mode RF prevented
from continuing to the shack.  The plastic box is important for this
-- a typical metal box would allow the shield RF to continue from the
UHF jack flanges around the relay at all times.  The relay I used has
a 24 v. coil because my T/R sequencing system runs on a 24 v. DC
supply.  This as all antenna relays should be used with a sequencer to
avoid hot switching.   Obviously this is not a solution if one desires
QSK.  In that case a faster switch is needed.

73

Rob
K5UJ
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: RX/TX Antenna decoupling, (OFF LIST)

[Rob Atkinson]

I discovered my rx antennas worked much better if my tx antenna was
completely disconnected from the station.  Most coaxial relays or T/R
switches only break the center conductor.   That's not good enough.
There has to be a complete disconnection which I provided by using an
open frame relay mounted in a plastic box.  On 160 m. such a device
will not present an impedance bump but this solution worked for me
because I don't care about QSK.  This may not be necessary if the tx
and rx antennas can be separated by one or more wavelengths.

73

Rob
K5UJ
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Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: RX/TX Antenna decoupling, (OFF LIST)

[MR TREVOR DUNNE]

Thanks Iain

That's what I am planning too hope it works out for both of us,

See you in the pile ups,

73
Trevor
EI2GLB
- Original Message -
From: iain haywood 
To: ei2...@eircom.net
Sent: Mon, 02 Oct 2017 17:31:18 +0100 (IST)
Subject: Topband: RX/TX Antenna decoupling, (OFF LIST)

Hi Trevor,

I have also seen your posts on other forums about this issue.

I am also installing an Rx antenna.

I am no expert for sure but I think the main reason is to stop the TX 
antenna being resonant and re-radiating noise etc. so the object is so 
make it non resonant (NOT a 1/4 wave)  on your band of choice.

I plan to short my inverted-L to the FCP counterpoise, (or other 
radial), this way it is electrically a 1/2 wave and shouldn't radiate on 
top band..

73

Iain G4SGX


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